Evidence that snakes may be a symbol of wisdom, fertility, and immortality are as follows
Fertility
- The oldest known representation of two snakes entwined around a rod is that of the Sumerian fertility god Ningizzida. According to Sumerian mythology, Ningizzida is the mother of Dumuzi (Tammuz) the god of spring vegetation and they both stood at the gate of heaven. Tamuz guarded the door of heaven and had the power of bestowing fertility. Source: Tower of Babel
The snake was also the sacred symbol of the god Ningizzida, who was called in Sumerian mythology “the companion of Tammuz. He was the guardian at the door of heaven who had the power to bestow fertility, “who protected the living by his magic spells, and could ward off death and heal disease for the benefit of those who worshiped him devoutly.” Source: Serpent Symbols
"In the Vodou of Benin and Haiti, Ayida-Weddo (a.k.a. Aida-Wedo, Aido Quedo, "Rainbow-Serpent") is a spirit of fertility, rainbows and snakes, and a companion or wife to Dan, the father of all spirits Source: The Book of Vodou.
Referring to Segal, Charles M. (1998). Aglaia: the poetry of Alcman, Sappho, Pindar, Bacchylides, and Corinna. Rowman & Littlefield. p. 91, the Gorgon at the the Temple of Artemis shown at the Archaeological Museum of Corfu is noted to wear a belt of intertwined snakes, a fertility symbol. Source: Corfu
Referring to Allocco, Amy Leigh. "Fear, Reverence And Ambivalence: Divine Snakes In Contemporary South India." Religions Of South Asia 7.(2013): 230-248
In Asia, South Indian Women gather at Hindu temples to worship Nagas (considered snake goddesses in south Indian Hinduism). At the temples, the Nagas take the form of snakes carved into stones. Hindu women gather around the stones to make offerings to the female snake goddesses. These goddesses are believed to make women fertile, protect the women and her family, and bring prosperity. The snake goddess is represented as an anthill or a snake that lives inside an anthill or stones with snake carvings on them. In each form, women honor the nāgas with offerings. Hindus in Tamil Nadu believe a person who harms or kills a snake will be inflicted with a condition known as nāga dösam which causes infertility and delays in marriage. Naga dosam can only be reversed through varying degrees of worship to naga.
The important Minoan deity is noted to be the mother earth goddess of the city-state Knossos, or Cnossus, the capital of Cretan civilization. She is same as the fertility goddesses worshiped elsewhere in ancient Mediterranean and Near Eastern cultures. On Crete she was shown in small statue form as a woman holding a snake in each hand with a bird perched on top of her head. Source: Snake Goddess.
"The cultic association of the bull with the serpent emphasizes the fertility aspect of
the serpent. The serpent-bull symbolism is widespread. Egypt, Mesopotamia, and Assyria have influenced the Canaanites at this point, and Palestine again becomes part of the larger Near East in its cultic symbolism."
Mortality
"Naga is the Sanskrit/Pāli word for a deity or class of entity or being, taking the form of a very large snake, found in Hinduism and Buddhism. The naga primarily represents rebirth, death and mortality, due to its casting of its skin and being symbolically "reborn". Brahmins associated naga with Shiva and with Vishnu, who rested on a 100 headed naga coiled around Shiva’s neck."
"As with the god Ningizzida, the Mesopotamian corn goddess, Nidaba, was shown in representations with serpents (springing from her shoulders). In the Sumerian and
Babylonian worldviews the serpent was symbolic of the regenerative and healing properties
of certain elements and produce of the earth."
"The spiral is a representation of the snake, which is an archetype for the cyclical mode of life."
Wisdom
"The most famous example of the winged serpent motif outside of (but related to) the Near East, namely, the Aztec god Quetzalcoatl (“feathered serpent”), is impressive because that god was revered as the founder of priestly wisdom. Quetzalcoatl’s high priests even bore the title “Prince of Serpents.”
Jesus purported statement in The Bible at Matthew 10:16 to be “wise as serpents”.
Researchers had also claimed to have identified signs of a 70,000-year-old African ritual practice linked to snake mythology of modern Botswanans which may be the earliest evidence for ritual behavior here. However, this finding has been challenged by the original researchers of the Rhino caves here.